Virtually no information about the pharmacokinetics of cyclosporine a (CSA) is available for patients with autoimmune diseases. This is significant because close monitoring of whole blood CSA concentrations is essential for the safe and effective management of CSA therapy. We have provided routine monitoring services of CSA whole blood through concentrations as well as occasional measurement of synovial fluid CSA concentrations in support of this study. In addition, the single dose pharmacokinetics of oral CSA, 1 mg/kg/day and 10 mg/kg/day respectively, were evaluated in 24 patients, equally divided between the low and high CSA doses. We delineated the pharmacokinetic parameter values which characterize CSA accumulation and disposition at the steady state. We were able to demonstrate that chronic CSA therapy does not affect its own metabolism and that single dose kinetics may be used to predict steady state blood CSA concentrations. This information may be useful in designing prospectively oral CSA dosage regimens.